Air-soil exchange of dimethyl sulfide, carbon disulfide, and dimethyl disulfide in three subtropical forests in south China

摘要

The exchange of dimethyl sulfide (DMS), carbon disulfide (CS2), and dimethyl disulfide (DMDS) between soil and the atmosphere was investigated in three subtropical forests in south China, namely, a monsoon evergreen broadleaf forest (BF) in climax successional stage, a pine and broadleaf mixed forest (MF) in midsuccessional stage, and a pine forest (PF) in primary successional stage. The forest soils acted as sources for DMS with average flux in BF (1.27 ± 1,40 pmol m~(-2) s~(-1)) significantly higher than those in MF (0.46 ± 0.30 pmol m~(-2) s~(-1)) or in PF (0.47 ± 0.36 pmol m~(-2) s~(-1)), Litter-removed plots showed 55%, 21%, and 53% lower DMS emission fluxes compared to litter-remained plots in BF, MF, and PF, respectively, suggesting the litter layer made evident contribution to DMS emission. DMS fluxes were significantly higher in rain seasons than in dry seasons. Dependence of DMS fluxes on soil temperature varied in the three forests, and significant correlations between DMS fluxes and soil temperature were only observed in BF and MF. No significant correlation was found between soil water content and DMS fluxes. However, DMS fluxes were found to be significantly correlated with soil temperature and water content together in polynomial forms with an order of 2. DMS fluxes were also exponentially correlated with CO_2 fluxes. CS_2 and DMDS fluxes showed no consistent direction. CS_2 fluxes varied between -8.51 and 4.72 pmol m~(-2) s~(-1) and DMDS fluxes between -0.25 and 2.00 pmol m~(-2) s~(-1), respectively. No clear patterns were found for the influence of litter layer on the CS_2or